Blender 2.9 won't open anymore
Locate and delete the preferences files for 2.9.
The files you need to delete are startup.blend, userpref.blend, bookmarks.txt, recent-files.txt.
Read this link to find them on your system.
Where is the startup file stored?
Re-install blender and disable all adons.  If the program runs, only then start adding addons one by one, until you find the one that is creating the problem.
Once you find the problem you can report the bug to the developer of that particular addon.
If none of this works, then run blender in debug mode and file a bug report with the info from the console.
Best place to put bug reports?